[Coco] Trying to get a KoKo2 working

[Arthur Flexser]

What you describe sounds like you're simply having trouble getting a
good contact between your ohmmeter and the ribbon cable traces.
Instead, try simply holding the ribbon cable up to a strong light in
back of the traces, which should reveal any breaks.

Art

On Sun, Aug 25, 2013 at 3:37 PM, Chris Osborn <fozztexx at fozztexx.com> wrote:
> Pulled apart the membrane and I can get continuity on the traces inside between keypads, but on the tail that comes out I can't get anything at all. I can pick any two spots on the same trace on the tail, and it never works. Doesn't really seem like a break since I would expect to get something until I hit a break, and I get nothing at all.
>
> On Aug 25, 2013, at 12:27 PM, Arthur Flexser wrote:
>
>> I think it's more likely that there are broken traces on the ribbon
>> cable.  Have you tested the continuity between the two ends on each
>> trace?
>>
>> A stuck joystick button can also prevent the keyboard from working.
>>
>> Art
>>
>> On Sun, Aug 25, 2013 at 3:06 PM, Chris Osborn <fozztexx at fozztexx.com> wrote:
>>> Thanks to Retro Canada I got a copy of the schematic and was able to test the PIA and the keyboard connector on the PCB and it's working fine. Pulled out a wire and jumpered the pins on the connector and I was able to "type". So it looks like the problem is entirely the plastic membrane inside of the keyboard. Is it possible it has become oxidized and if so, can it be cleaned? It has a black coating on all the traces and I had to scratch through it a little bit for the DMM probe to get a signal. I'm afraid of scraping it off though and having no trace left.
>>>
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